Major Blood Vessels Click Image to Enlarge Normal function of the brain’s control centers is dependent upon adequate supply of oxygen and nutrients through a dense network of blood vessels. Blood is supplied to the brain, face, and scalp via two major sets of vessels: the right and left common carotid arteries and the right and left vertebral arteries. The common carotid arteries have two divisions. The external carotid arteries supply the face and scalp with blood. The internal carotid arteries supply blood to most of the anterior portion of the cerebrum. The vertebrobasilar arteries supply the posterior two-fifths of the cerebrum, part of the cerebellum, and the brain stem. Any decrease in the flow of blood through one of the internal carotid arteries brings about some impairment in the function of the frontal lobes. This impairment may result in numbness, weakness, or paralysis on the side of the body opposite to the obstruction of the artery. Occlusion of one of the vertebral arteries can cause many serious consequences, ranging from blindness to paralysis.

Click Image to Enlarge Circle of Willis At the base of the brain, the carotid and vertebrobasilar arteries form a circle of communicating arteries known as the Circle of Willis. From this circle, other arteries—the anterior cerebral artery (ACA), the middle cerebral artery (MCA), the posterior cerebral artery (PCA)—arise and travel to all parts of the brain. Posterior Inferior Cerebellar Arteries (PICA), which branch from the vertebral arteries, are not shown. Because the carotid and vertebrobasilar arteries form a circle, if one of the main arteries is occluded, the distal smaller arteries that it supplies can receive blood from the other arteries (collateral circulation). Click Image to Enlarge Anterior Cerebral Artery The anterior cerebral artery extends upward and forward from the internal carotid artery. It supplies the frontal lobes, the parts of the brain that control logical thought, personality, and voluntary movement, especially of the legs. Stroke in the anterior cerebral artery results in opposite leg weakness. If both anterior cerebral territories are affected, profound mental symptoms may result (akinetic mutism).

Middle Cerebral Artery The middle cerebral artery is the largest branch of the internal carotid. The artery supplies a portion of the frontal lobe and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, the areas for speech. Click Image to Enlarge The middle cerebral artery is the artery most often occluded in stroke. Posterior Cerebral Artery The posterior cerebral arteries stem in most individuals from the basilar artery but sometimes originate from the ipsilateral internal carotid artery [Garcia JH et al., In Barnett HJM at al (eds) Stroke Pathophysiology, Diagnosis, and Management New York Churchill Livingstone 1992 125]. The posterior arteries supply the temporal and occipital lobes of the left cerebral hemisphere and the right hemisphere. When infarction occurs in the territory of the posterior cerebral artery, it is usually secondary to embolism from lower segments of the vertebral basilar system or heart.

Click Image to Enlarge Clinical symptoms associated with occlusion of the posterior cerebral artery depend on the location of the occlusion and may include thalamic syndrome, thalamic perforate syndrome, Weber’s syndrome, contralateral hemplegia, hemianopsia and a variety of other symptoms, including including color blindness, failure to see to-and-fro movements, verbal dyslexia, and hallucinations. The most common finding is occipital lobe infarction leading to an opposite visual field defect. Lenticulostriate Arteries Small, deep penetrating arteries known as the lenticulostriate arteries branch from the middle cerebral artery Occlusions of these vessels or penetrating branches of the Circle of Willis or vertebral or basilar arteries are referred to as lacunar strokes. About 20% of all stokes are lacunar [Stoke/Brain Attack reporter’s Handbook. Englewood, Colo: National Stroke Association, 1995] and have a high incidence in patients with chronic hypertension.

Click Image to Enlarge In the elderly, CT scanning shows signs of infarction in only approximately half of the most of the common form of lacunar stroke (pure motor stroke), but MRI has increased the yield: the probability that CT or MRI will be positive is generally a function of the severity of the deficit [Mohr JP and Sacco RL, 1992]. The cells distal to the occlusion die, but since these areas are very small often only minor deficits are seen. When the infarction is critically located, however, more severe manifestations may develop, including paralysis and sensory loss. Within a few months of the infarction, the necrotic brains cells are reabsorbed by macrophage activity, leaving a very small cavity referred to as a lake (or lacune in French). Credits Cardiovascular System of the Head and Neck Home > Cardiovascular System > Cardiovascular System of the Head and Neck Cardiovascular System of the Head and Neck The cardiovascular system of the head and neck includes the vital arteries that provide oxygenated blood to the brain and organs of the head, including the mouth and eyes. It also includes the veins that return deoxygenated blood from these organs to the heart.

Among these blood vessels are several unique and important structures that have evolved to help maintain the continuous flow of blood to the brain. The human brain is so powerful and metabolically active that it uses about 20% of all of the oxygen and glucose taken in by the body each day.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Cardiovascular System of the Head and Neck Description [Continued from above] . . . Any interruption in the blood flow to the brain very quickly results in the decline of mental function, loss of consciousness, and eventually death if not corrected. Oxygenated blood enters the neck from the trunk through four major arteries: the left and right vertebral arteries and the left and right common carotid arteries. The vertebral arteries travel through the transverse foramina of the cervical vertebrae before entering the skull at the foramen magnum and joining at the base of the brain to form the basilar artery.

From there the basilar artery provides blood to the posterior structures of the brain, including the brain stem, cerebellum, and cerebrum. The left and right carotid arteries each divide in the neck to form the left and right internal carotid as well as the left and right external carotid arteries. The internal carotid arteries pass into the skull inferior to the brain through the left and right carotid foramina. At the base of the brain, the internal carotid arteries branch off into the left and right anterior cerebral arteries and the left and right middle cerebral arteries that supply blood to the middle and anterior regions of the brain. At the base of the brain several communicating arteries form anastomoses, or passages, between the left and right posterior cerebral, left and right internal carotid, and left and right anterior cerebral arteries. These arteries collectively form a ring of blood vessels known as the Circle of Willis. The Circle of Willis provides insurance that the brain will continue to receive blood flow in the event that one of its major arteries is blocked by allowing blood flow between all of the major arteries to all of the regions of the brain.

In the neck and head exterior to the skull, the external carotid artery provides blood flow to the skin, muscles, and organs. Several major arteries - including the facial, superficial temporal, and occipital arteries - branch off from the external carotid to provide blood to the many superficial structures of the head. Three pairs of major veins return deoxygenated blood from the tissues of the head and neck to the heart. The left and right vertebral veins descend through the transverse foramina of the cervical vertebrae to drain blood from the spinal cord, cervical vertebrae, and muscles of the neck. In the head, superficial structures on the exterior of the skull are drained by the pair of external jugular veins, which descend through the neck lateral to the vertebral veins. Most importantly, the brain is drained by a group of large cavities in the dura mater layer of the meninges known as dural venous sinuses. Blood collected in these sinuses drains into the largest veins in the head and neck - the left and right internal jugular veins. The internal jugular veins collect blood from the brain as well as the superficial structures of the head and neck before descending through the neck towards the heart.

Prepared by Tim Taylor, Anatomy and Physiology Instructor Neuroscience For Kids - blood supply of the brain you are here: home > explore > blood supply Neuroscience For Kids The Blood Supply of the Brain Food and oxygen are carried to the brain by many blood vessels. These vessels are found on the surface of the brain and deep within the brain. The blood vessels (and nerves) enter the brain through holes in the skull called foramina Although the brain is only about 2% of the total body weight in humans, it receives 15-20% of the body's blood supply. Because brain cells will die if the supply of blood which carries oxygen is stopped, the brain has top priority for the blood. Even if other organs need blood, the body attempts to supply the brain with a constant flow of blood. The blood brings many materials necessary for the brain to function properly. The blood also removes materials from the brain. Blood is supplied to the entire brain by 2 pairs of arteries: the internal carotid arteries and vertebral arteries. As you can see in the figure below, the right and left vertebral arteries come together at the base of the brain to form a single basilar artery.

The basilar artery joins the blood supply of the internal carotid arteries in a ring at the base of the brain. This ring of arteries is called the circle of Willis. The circle of Willis provides a safety mechanism...if one of the arteries gets blocked, the "circle" will still provide the brain with blood. Base of the Brain Only some of the vessels that exist in a real brain have been labeled. Brain Attack = Stroke You may know someone, a parent or grandparent, who has had a "stroke," also called a "brain attack." What exactly is a stroke? A stroke occurs when the blood supply to the brain is stopped. If this happens for enough time, neurons will start to die because they will not get enough oxygen. Paralysis or aphasia (loss of speech) are possible consequences of a stroke. There are two major causes of a stroke: 1.

Blockage of a blood vessel (in the brain or neck) caused by: a blood clot in the brain or neck (this is called a thrombosis) a blood clot from somewhere else that has moved and now blocks a blood vessel in the brain or neck (this is called an embolism) constriction or narrowing of an artery in the head or neck (this is called a stenosis) 2. Bleeding of a blood vessel (this is called hemorrhagic stroke) There are several warning signs that occur with a brain attack. (Reprinted with permission from The National Institute of Neurological Disorders and Stroke Sudden weakness or numbness of the face, arm, or leg on one side of the body. Sudden dimness or loss of vision, particularly in one eye. Sudden difficulty speaking or trouble understanding speech. Sudden severe headache with no known cause. Unexplained dizziness, unsteadiness, or sudden falls, especially with any of the other signs. There are several conditions linked to stroke. Reprinted with permission from The National Institute of Neurological Disorders and Stroke High blood pressure - Eat a balanced diet, maintain a healthy weight, and exercise to reduce blood pressure. Drugs are also available.

Cigarette smoking - Don't start smoking and if you do smoke, quit! Heart disease - Your doctor will treat your heart disease and may also prescribe medication to help prevent the formation of clots. Diabetes - Treatment can delay complications that increase the risk of stroke. Transient ischemic attacks - These are brief episodes of stroke's warning signs and can be treated with drugs or surgery. Did you know? Each year there are 700,000 people (one every 45 seconds) in the United States who suffer a stroke. Stroke is the THIRD leading cause of death in the US and kills about 160,000 Americans each year. (Statistic from American Stroke Association The word "carotid" (carotid artery) comes from the Greek word karotis meaning "deep sleep." This is because it has been known for a long time that pressure to the carotid arteries causes animals to become sleepy. In humans, the brain uses 15-20% of the body's oxygen supply. In the African elephant nose fish, the brain uses 60% of the oxygen supply!

(Source: Nilsson, G.E., Brain and body oxygen requirements of Gnathonemus perterssi, a fish with an exceptionally large brain. J. Experi. Biol., 199:603-607, 1996.) More about stroke: Blood Supply (Arteries and Veins) of Head and Neck | NEURON ARC Blood Supply (Arteries and Veins) of Head and Neck June 24, 2012 | By neuron arc | Reply More Blood Supply (Arteries and Veins) of Head and Neck Blood supply- Arteries The arterial supply of the head and neck is derived from the common carotid The right common carotid arises from the brachiocephalic trunk. The left common carotid arises from the aortic arch directly. The common carotid runs upwards in the neck to the upper border of the thyroid cartilage. Then it divides into external and internal carotid arteries. The external carotid artery The external carotid artery provides the major blood supply for the face and mouth. The two major terminal branches of the external carotid artery are the maxillary and the facial arteries.

The maxillary artery is the large of the two terminal branches of the external carotid artery. The maxillary artery It arises behind the angle of the mandible and supplies the deep structures of the face. Major branches of the maxillary artery: 1. Infraorbital artery 2. Posterior superior alveolar artery 3. Inferior alveolar artery Infraorbital artery gives branches to anterior and middle superior alveolar arteries. Their distribution to the maxillary incisors and cuspid teeth and to the maxillary sinuses. Posterior superior alveolar artery. Its distribution is to the maxillary molar and premolar teeth and gingiva. Inferior alveolar artery. It descends close to the medial surface of the mandibular ramus to the mandibular foramen. Before entering the foramen, it gives off the mylohyoid branch which supplies tissues in the floor of the mouth. The facial artery The facial artery is the other major branch of the external carotid artery. It enters the face at the inferior border of the mandible . It passes forward and upward across the cheek towards the angle of the mouth.

It continues upward along the side of the nose and ends at the medial canthus (inner corner) of the eye. The lingual artery also is a branch of the external carotid artery. Its distribution is along the surface of the tongue The internal carotid artery The internal carotid artery has a dilation at its root, the carotid sinus. The internal carotid artery has no branches outside the skull and enters the skull through the carotid canal. Inside the skull the internal carotid artery gives off the ophthalmic artery which supplies the optic nerve, eye, orbit and scalp MAJOR VEINS Head and neck major veins drainage The venous drainage of the head and neck begins as drainage of the brain. The superior and inferior sagittal sinuses drain to the transverse then sigmoid sinuses to form the internal jugular vein. The ophthalmic veins from the orbit drain backwards to the cavernous sinus or forwards to the facial vein. Head and neck major veins The cavernous sinus drains to the pterygoid plexus of veins, through the superior petrosal sinus to the transverse sinus and through the inferior petrosal sinus to the internal jugular vein 1.

Facial vein What are the carotid arteries? - Heart & Circulatory System - Sharecare What are the carotid arteries? Topics | Heart and Circulatory System | What are the carotid arteries? A Answers (7) A SCAI answered The carotid arteries are two large blood vessels located toward the front of the neck that carry blood to the brain. Blood reaches the carotid arteries by traveling from the heart and passing through a large artery called the aorta. Then the blood moves through the carotid arteries to the brain. Each of the carotid arteries splits into two separate arteries near the top of the neck to form the left and right internal and external carotid arteries. The larger of these two branched arteries, called the internal carotid artery, delivers oxygenated blood to portions of your brain responsible for cognition, speaking, and motor skills. As a result, stroke victims often suffer from deficits in these areas. A Dr. William D. Knopf, MD , Cardiology (Cardiovascular Disease), answered on behalf of Piedmont Heart Institute The carotid artery is a major artery that carries blood from the heart to the head.

There is a carotid artery on each side of the neck, and each one splits into two branches. The interior branch carries blood to the brain and eyes, and the exterior branch carries blood to the face, tongue, and outside parts of the head. A American Academy of Ophthalmology's EyeSmart answered The carotid (pronounced ka-RAH-tid) arteries are located in your neck and are the main arteries supplying blood to the eyes and brain. There are two carotid arteries: one on the right side of the neck (which supplies blood to the right side of the brain) and one on the left side of the neck (which supplies blood to the left side of the brain). When blood flowing through the carotid artery is reduced or blocked, the eyes and brain do not receive enough oxygen. As a result, brain function and vision can be greatly affected. A Brigham and Women's Hospital answered The carotid arteries are paired arteries in the neck that serve as the major blood supply to the brain. Carotid Artery Disease is when one or both arteries in your neck become narrowed due to accumulation of plaque. Blockages in these arteries can lead to stroke or other problems with brain circulation. A Dr.

Mehmet Oz, MD , Cardiology (Cardiovascular Disease), answered The carotid arteries are the main arteries on either side of your neck that supply the head and neck with oxygenated blood. You have two carotid arteries, one on the left side of your neck and one on the right side. If you put your fingertips on the side of your neck, you will feel a pulse. That is your carotid artery. The carotid arteries divide into internal and external carotid arteries. The job of the internal carotid arteries is to supply oxygen-rich blood to the brain. The external carotid arteries supply blood to the face, scalp, and neck. Helpful? 1 person found this helpful. A NewYork-Presbyterian Hospital answered The carotid arteries provide the brain with most of its blood supply and are located in the neck on either side of the windpipe.

Major Arteries of the Head and Neck - Carotid - TeachMeAnatomy Major Arteries of the Head and Neck Original Author: Oliver Jones Last Updated: August 14, 2016 Revisions: 39 The head and neck receives the majority of its blood supply through the carotid and vertebral arteries. This article shall explore the anatomy of this arterial system – its anatomical course, branches, and clinical correlations. Carotid Arteries © 2015-2017 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.0 – Origin of the blood vessels of the upper limb. Note how the left common carotid and subclavian arteries arise directly from the arch of aorta. We shall start at the origin of the carotid arteries. The right common carotid artery arises from a bifurcation of the brachiocephalic trunk (the right subclavian artery is the other branch). This bifurcation occurs roughly at the level of the right sternoclavicular joint. The left common carotid artery branches directly from the arch of aorta.

The left and right common carotid arteries ascend up the neck, lateral to the trachea and the oesophagus. They do not give off any branches in the neck. At the level of the superior margin of the thyroid cartilage (C4), the carotid arteries split into the external and internal carotid arteries. This bifurcation occurs in an anatomical area known as the carotid triangle . The common carotid and internal carotid are slightly dilated here, this area is known as the carotid sinus, and is important in detecting and regulating blood pressure. © 2015-2017 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.1 – Lateral vein of the neck, showing the origin and bifurcation of the common carotid artery. Clinical Relevance: Carotid Sinus Hypersensitivity The carotid sinus is a dilated portion of the common carotid and internal carotid arteries. It contains specific sensory cells, called baroreceptors. The baroreceptors detect stretch as a measure of blood pressure.

The glossopharyngeal nerve feeds this information to the brain, and this is used to regulate blood pressure. In some people, the baroreceptors are hypersensitive to stretch. In these patients, external pressure on the carotid sinus can cause slowing of the heart rate and a decrease in blood pressure. The brain becomes underperfused, and syncope results. In such patients, checking the pulse at the carotid triangle is not advised. External to the carotid sinus, there is a cluster of nervous cells, called the carotid body. These act as peripheral chemoreceptors; detecting the O2 content of the blood, and relaying this information to the brain to regulate breathing rate. External Carotid Artery The external carotid artery supplies the areas of the head and neck external to the cranium. After arising from the common carotid artery, it travels up the neck, posterior to the mandibular neck and anterior to the lobule of the ear. The artery ends within the parotid gland, by dividing into the superficial temporal artery and the maxillary artery.

Before terminating, the external carotid artery gives off six branches: Superior thyroid artery Occipital artery Posterior auricular artery The facial, maxillary and superficial temporal arteries are the major branches of note. The maxillary artery supplies the deep structures of the face, while the facial and superficial temporal arteries generally supply superficial areas of the face. Clinical Relevance: Blood Supply to the Scalp The posterior auricular, occipital and superficial temporal arteries (along with two branches of the internal carotid artery; supra-orbital and supratrochlear) combine to provide a dense blood supply to the scalp. Injuries to the scalp can cause excessive bleeding for various reasons: The walls of the arteries are tightly and closely bound to the underlying connective tissue of the scalp. This prevents them from constricting to limit blood loss following injury or laceration. The numerous anastomoses formed by the arteries produce a very densely vascularised area. Deep lacerations can involve the epicranial aponeurosis, which is worsened by the opposing pulls of the occipital and frontalis muscles.

Despite the possible heavy bleeding, it is important to note that the bony skull gets its blood from an alternative source (middle meningeal artery), and so will not undergo avascular necrosis. © 2015-2017 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.3 – Lateral view of the skull, showing the path of the meningeal arteries. Note the pterion, a weak point of the skull, where the anterior middle meningeal artery is at risk of damage. Internal Carotid Artery The internal carotid arteries do not supply any structures in the neck, entering the cranial cavity via the carotid canal in the petrous part of the temporal bone. Within the cranial cavity, the internal carotid artery supplies: The brain Forehead Clinical Relevance: Atherosclerosis of the Carotid Arteries The swelling at the bifurcation of the common carotid arteries, the carotid sinus, produces turbulent blood flow. This increases the risk of atheroma formation in this area, with the internal carotid more susceptible than the others.

Atherosclerotic thickening of the tunica intima of these arteries will reduce blood flow to the brain, resulting in the variety of neurological symptoms; headache, dizziness, muscular weakness. If blood flow is completely occluded, a cerebral ischaemia (stroke) results. If atherosclerosis of the carotid arteries is suspected, a Doppler study can be used to assess the severity of any thickening. In severe cases, the artery can be opened, and the atheromatous tunica intima removed. This procedure is called a carotid endarterectomy. Vertebral Arteries © 2015-2017 TeachMeAnatomy.com [CC-BY-NC-ND 4.0] Fig 1.4 – Blood supply to the brain via the vertebral arteries The right and left vertebral arteries arise from the subclavian arteries, medial to the anterior scalene muscle. They then ascend up the posterior side of the neck, through holes in the transverse processes of the cervical vertebrae, known as foramen transversarium. The vertebral arteries enter the cranial cavity via the foramen magnum, and converge.

They then give rise to the basilar arteries, which supply the brain. The vertebral arteries supply no branches to the neck, or extra-cranial structures. Other Arteries of the Neck The neck is supplied by arteries other than the carotids. The right and left subclavian arteries give rise to the thyrocervical trunk. From this trunk, several vessels arise, which go on to supply the neck. The first branch of the thyrocervical trunk is the inferior thyroid artery. It supplies the thyroid gland The ascending cervical artery arises from the inferior thyroid artery, as it turns medially in the neck. This vessel supplies the posterior prevertebral muscles. The transverse cervical artery is the next branch off the thyrocervical trunk. It crosses the base of the carotid triangle, and supplies the trapezius and rhomboid muscles. Lastly, the suprascapular artery arises. It supplies the posterior shoulder area.

Fig 1.5 – Lateral view of the neck, showing the thyrocervical trunk Medical Aspects: Blood Supply The Neuroscience on the Web Series: SPPA 636 Neuropathologies of Language and Cognition CSU, Chico, Patrick McCaffrey, Ph.D. Chapter 4. Medical Aspects: Blood Supply to the Brain Blood Supply to the Brain The consequences of stroke depend upon which areas of the brain are affected by ischemia, hemorrhage, hematoma or aneurysm. Therefore, it is important to understand the organization of the cerebral blood supply system. Two arterial systems supply the brain with blood: the internal carotid and basilar. The internal carotids and basilar arteries are connected via the circle of Willis , which allows blood to pass from one system to another in the event of blockage. The Internal Carotid Arteries There are two internal carotid arteries. They ascend from the aortic arch toward the brain along each side of the neck. They pass behind the ear into the temporal lobe and enter the subarachnoid space.

They then go to the circle of Willis where each bifurcates to form two main branches: the anterior cerebral artery and the middle cerebral artery. The course of the internal carotid arteries and their branches is tortuous. Because of their many twists and turns these arteries are all subject to blockages caused by cholesterol build-up. For this reason, the internal carotids, and the middle and anterior cerebral arteries are more vulnerable to ischemic rather than hemorrhagic stroke. According to FitzGerald, 1996, the contralateral internal carotid may use the circle of Willis/anterior communicating artery to supply blood to both pairs of anterior and middle cerebral arteries. Complete interruption of blood flow in the anterior cerebral artery is not very likely because the opposite anterior cerebral can use the anterior communicating artery to make up for the deficiency. Even the facial artery (external carotid) can shunt blood to the anterior and middle cerebral arteries via the ophthalmic artery. The Anterior Cerebral Arteries The anterior cerebral arteries supply blood to the medial cortex, including the medial aspects of the motor and sensory strips.

Due to the upside-down representation of the homunculus in both of these area, a blockage in an anterior cerebral artery could cause paralysis or sensory deficits which affect the opposite side of the body from the hips on down. For example, a patient who has suffered such a blockage might have a paralyzed leg or be incontinent of bowel and/or bladder. Since the parts of the motor and sensory strips connected to the arm receive some blood from the anterior cerebral artery, the arm may also be somewhat affected by this kind of blockage. Finally, apraxia of gait may also occur if an anterior cerebral artery fails to supply an adequate amount of blood to the medial part of the motor strip. The anterior cerebral arteries also supply blood to the anterior aspects of the frontal lobes. As these areas are involved in higher level cognition such as reasoning and judgment, a condition called cerebral dementia may result from anterior cerebral artery blockages. Confused language , or a language indicative of cognitive impairment, may also occur. The Middle Cerebral Arteries These large arteries have tree-like branches that bring blood to most of the lateral cortex of each cerebral hemisphere. This means that the middle cerebral arteries supply blood to the cortical areas involved in speech, language and swallowing.

The left middle cerebral artery provides Broca's area , Wernicke's area , Heschl's gyrus, and the angular gyrus with blood. Also, the "head" and "neck" areas of the motor and sensory strips in both hemispheres receive their blood supply from the middle cerebral arteries. Damage to these cortical areas on either side of the brain can impair motor speech and swallowing functions. In addition, the middle cerebral arteries provide most of the blood supply to the corpus striatum . The striatas, which are arterial branches of the middle cerebral arteries, are known as the arteries of stroke as they are the main source of blood for the internal capsule. A rupture of the lenticulo-striate artery results in bleeding usually in the region of the internal capsule (Steadman, 1997). When one of these arteries is damaged, the bottleneck of fibers within the internal capsule , including the pyramidal tract, can be affected, causing many disabilities. The striatas have relatively thin walls and pressure within them is high. For this reason, they are more vulnerable to hemorrhages than to blockages.

Because the middle cerebral arteries supply blood to so many areas of the brain, blockages in this part of the circulatory system can cause numerous types of disorders. If the left middle cerebral artery is blocked, aphasia and apraxia may occur. Blockages of the right middle cerebral artery can cause left side neglect, which is an impairment in the ability to recognize and respond to stimuli on the left side of the body, prosopagnosia or the inability to recognize faces, and various cognitive problems, including agnosia. All of these are part of the right hemisphere syndrome. Blockages of either middle cerebral artery can cause contralateral hemiplegia or hemiparesis as well as contralateral hyposthesia. Paralysis and sensory deficits will affect the head and neck most. Because the "hand" and "arm" areas are superior to the "head" and "neck" areas of the pre and postcentral gyri, they receive some blood supply from the anterior cerebral arteries. For this reason, they may not suffer as much after a middle cerebral artery blockage.

Damage to the internal capsule caused by blockage or hemorrhage of the striata (branch of middle cerebral) can cause upper motor neuron dysarthria and dysphagia. In addition, damage to either middle cerebral artery can cause hemianopsia or the loss of sight in one half of the visual field. This blindness affects the contralateral aspect of both visual fields. For example, a blockage in the right middle cerebral artery will cause left hemianopsia or blindness in the left visual field of both eyes. The Vertebro-Basilar System Both of the vertebral arteries ascend through the spinal column and enter the brain through the magnum foramen. Once in the brain, they continue to ascend, traveling beside the brain stem. At the lower border of the pons the two vertebral arteries join together to form the basilar artery or vertebro-basilar artery. The vertebral arteries and the basilar are straight arteries and therefore not as subject to blockages due to the build up of cholesterol as are the internal carotids. The posterior inferior cerebellar not only supply the cerebellum but take blood to the lateral medulla.

Anterior and posterior spinal arteries supply the ventral and dorsal medulla, respectively (FitzGerald 1996). The three arteries are branches of the vertebral. The side of the pons and the cerebellum receive blood from the anterior inferior cerebellar artery and the superior cerebellar artery. These arteries are branches of the basilar. The anterior inferior cerebellar artery also has a branch, the labyrinthine artery, that supplies the inner ear. The basilar also gives off about twelve pontine arteries that supply the medial pons (FitzGerald, 1996). At the superior border of the pons, the basilar artery divides to form the two posterior cerebral arteries. Before the basilar artery divides, several other arteries arise from it. These include the anterior, inferior, and posterior cerebellar arteries as well as pontine branches. So, the cerebellum and pons are mainly supplied by branches of the basilar. The Posterior Cerebral Arteries At the superior border of the pons, the basilar artery divides to form the two posterior cerebral arteries.

These arteries supply blood to the part of the brain that lies in the posterior fossa of the skull, including the medial aspects of the occipital lobes , the inferior portions of the temporal lobes , the brainstem, and the cerebellum . They also deliver blood to the thalamus and some other subcortical structures. A vascular lesion may result in Thalamic Aphasia or Thalamic Syndrome where the posterior thalamic nucleus is disconnected from the sensory cortex. This rare syndrome causes complete contralateral sensory loss alternating with bouts of severe pain (FitzGerald, 1997). As the vertebral and basilar are somewhat wide arteries and their course is relatively straight, they are not as subject to blockages caused by the build-up of cholesterol as the internal carotids. This means that, overall, cerebrovascular accidents effect the basilar system less frequently than the internal carotid system. However, the basilar and posterior cerebral arteries may hemorrhage due to shearing injuries caused by accidents or pressure due to edema of the brain.

Since they provide blood to the occipital lobes, damage to these arteries can cause a variety of visual problems, including cortical blindness and alexia, which is an inability to read and visual agnosia, or the inability to recognize stimuli presented visually. Because these arteries supply blood to the cerebellum and to the brain stem, blockages or hemorrhaging there can cause either ataxic (cerebellar) or flaccid (lower motor neuron) dysarthria . . It is important to note that the effects of ischemic stroke are almost always contralateral and therefore unilateral. On the other hand, hemorrhagic strokes may damage both hemispheres, depending upon the size and location of the resulting hematoma. One exception to this pattern is alternating hemiplegia. This is a paralysis that can be caused by ischemic stroke and affects different structures on each side of the body. It results from a brain stem lesion that damages cranial nerve nuclei and one side of the pyramidal tract in the same area. Lesions of cranial nerve nuclei will cause a paralysis of the structures served by that nerve on the same side of the body as the injury.

Because the pyramidal tract provides only contralateral innervation to the spinal nerves, damage to these fibers will cause a paralysis of different structures on the other side of the body. For example, a lesion that affects the right nucleus of the trigeminal nerve and the right half of the pyramidal tract will cause paralysis of the right side of the jaw and of the skeletal muscles on the left side of the body. The Circle of Willis The Circle of Willis or the Circulus Arteriosus is the main arterial anastomatic trunk of the brain. According to Bhatnagar and Andy (1995), anastomosis occurs when vessels bring blood to one spot and then redistribute it. The two internal carotid arteries and the basilar arteries feed into the Circle of Willis. The blood is then redistributed by the anterior, middle and posterior cerebral arteries. Thus, the ends of the internal carotids and the basilar artery enter the Circle while the three cerebral arteries arise and exit from it. (Neither the internal carotids nor the basilar arteries can be considered "cerebral" arteries since they do not begin within the brain).

In the Circle of Willis the two internal carotids are joined together by the anterior communicating artery while the posterior communicating artery links the internal carotid system with the basilar artery. These connections make collateral circulation, which Love and Webb (1992, p. 40) define as "the flow of blood through an alternate route," possible. This is a safety mechanism, allowing brain areas to continue receiving adequate blood supply even when there is a blockage somewhere in an arterial system. When all arteries are functioning normally, their blood supplies will not mix where they meet in the Circle because the pressure of their streams will be equal. As long as the Circle of Willis can maintain blood pressure at fifty percent of its normal level, no infarction or death of tissue will occur in an area where a blockage exists. If collateral circulation is good, sometimes a blockage will have no permanent effects. Sometimes, an adjustment time is required before collateral circulation can reach a level that supports normal functioning; the communicating arteries will enlarge as blood flow through them increases. In such cases, a transient ischemic attack may occur, meaning that parts of the brain are temporarily deprived of oxygen. Collateral circulation is not always sufficient to prevent a stroke.

Some people lack one or more of the communicating arteries in the Circle of Willis. This means that, if a blockage develops, blood cannot be redistributed from another arterial system and stroke will occur. FitzGerald (1996), writes that 25% of people get blood to their posterior cerebral arteries from the internal carotids, rather than from the vertebro-basilar system. Also, even when all the communicating arteries exist, the influence of several extraneural factors including abnormal blood pressure, cerebrovascular resistance, and arteriosclerosis may impede collateral circulation. Low blood pressure, which can result from surgical shock, may prevent blood from traveling through the smaller diameter arteries. Pressure or hypertension can cause stenosis of the arteries by pushing plaque up against their walls. Cerebrovascular resistance makes it more difficult for blood to flow from one area to another. It can be caused by arterial spasm, a high level of tri-glycerides in the blood which increases its viscosity, or by elevated levels of cerebral spinal fluid. Arteriosclerosis or the formation of "plaque" consisting of muscle cells and blood cells, as well as fats on arterial walls also makes it more difficult for blood to flow through communicating arteries.

Watershed Areas Parts of the brain located at the ends of the distribution areas of the vascular systems are called the watershed areas. According to Bhatnager and Andy (1995, p.345), a watershed area is a "tertiary brain area located peripheral to primary distribution areas for anterior, posterior, and middle cerebral arteries; it derives blood via the branches of all three cortical arteries." Because they are at the extreme ends of arterial distribution they are particularly vulnerable to ischemia and infarction in those who have circulation problems. Lesions in the watershed areas may cause transcortical sensory aphasia. Blood Supply to the Head and Neck Blood Supply to the Head and Neck Advertisements help pay for this website. Thank you for your support. Last updated 30 March 2006 Blood Supply to the Head and Neck Most arteries in the anterior cervical triangle arise from the common carotid artery or one of the branches of the external carotid artery. Click here for blood supply to the brain. Most veins in the anterior cervical triangle are tributaries of the large internal jugular vein. Click here for the venous sinuses of the dura mater. The Common Carotid Arteries (p.

804) The right common carotid artery begins at the bifurcation of the brachiocephalic trunk, posterior to the right sternoclavicular joint. The left common carotid artery begins arises from the arch of the aorta and ascends into the neck, posterior to the left sternoclavicular joint. Each common carotid artery ascends into the neck within the carotid sheath to the level of the superior border of the thyroid cartilage. Here it terminates by dividing into the internal and external carotid arteries. Back to top The Internal Carotid Artery (p. 804) This is the direct continuation of the common carotid artery and it has no branches in the neck. It supplies structures inside the skull. The internal carotid arteries are two of the four main arteries that supply blood to the brain. Each artery arises from the common carotid at the level of the superior border of the thyroid cartilage. It then passes superiorly, almost in a vertical plane, to enter the carotid canal in the petrous part of the temporal bone. A plexus of sympathetic fibres accompany it.

During its course through the neck, the internal carotid artery lies on the longus capitis muscle and the sympathetic trunk. The External Carotid Arteries (p. 805) Click here for a diagram of the external carotid artery and its branches. This vessel begins at the bifurcation of the common carotid, at the level of the superior border of the thyroid cartilage. It supplies structures external to the skull. The external carotid artery runs posterosuperiorly to the region between the neck of the mandible and the lobule of the auricle. It terminates by dividing into two branches, the maxillary and superficial temporal arteries . The stems of most of the six branches of the external carotid artery are in the carotid triangle. The Superior Thyroid Artery (p. 805) This is the most inferior of the 3 anterior branches of the external carotid. It arises close to the origin of the vessel, just inferior to the greater horn of the hyoid. The superior thyroid artery runs anteroinferiorly, deep to the infrahyoid muscles and gives off the superior laryngeal artery.

This artery pierces the thyrohyoid membrane in company with the internal laryngeal nerve and supplies the larynx . The Lingual Artery (p. 805) This arises from the external carotid artery as it lies on the middle constrictor muscle of the pharynx. It arches superoanteriorly, about 5 mm superior to the tip of the greater horn of the hyoid bone, and then passes deep to the hypoglossal nerve, the stylohyoid muscle, and the posterior belly of digastric muscle. It disappears deep to the hyoglossus muscle. At the anterior border of this muscle, it turns superiorly and ends by becoming the deep lingual artery. The Facial Artery (p. 805) This arises from the carotid artery either, in common with the lingual artery, or immediately superior to it. In the neck the facial artery gives off its important tonsillar branch and branches to the palate and submandibular gland. The facial artery then passes superiorly under the cover of the digastric and stylohyoid muscles and the angle of the mandible.

It loops anteriorly and enters a deep groove in the submandibular gland. The facial artery hooks around the inferior border of the mandible and enters the face. Here the pulsation of this artery can be felt (anterior to the masseter muscle). Click here to go the facial artery in the face. The Ascending Pharyngeal Artery (p. 805) This is the 1st or 2nd branch of the external carotid artery. This small vessel ascends on the pharynx, deep to the internal carotid artery. It sends branches to the pharynx, prevertebral muscles, middle ear and meninges. The Occipital Artery (pp. 805-6) This arises from the posterior surface of the external carotid near the level of the facial artery. It passes posteriorly along the inferior border of the posterior belly of digastric . It ends in the posterior part of the scalp. During its course, it is superficial to the internal carotid artery and three cranial nerves (CN IX, CN X and CN XI). The Posterior Auricular Artery (p.

806) This is a small posterior branch of the external carotid artery. It arises from it at the superior border of the posterior belly of the digastric muscle. It ascends posteriorly to the external acoustic meatus and supplies adjacent muscles, the parotid gland, the facial nerve, structures in the temporal bone, the auricle, and the scalp. The Internal Jugular Vein (pp. 806-7) Click here for a diagram on the internal jugular vein and its tributaries. This is usually the largest vein in the neck. The internal jugular vein drains blood from the brain and superficial parts of the face and neck. Its course corresponds to a line drawn from a point immediately inferior to the external acoustic meatus to the medial end of the clavicle. This large vein commences at the jugular foramen in the posterior cranial fossa, as the direct continuation of the sigmoid sinus. The dilation at its origin is called the superior bulb of the internal jugular vein. From here it runs inferiorly through the neck in the carotid sheath. The internal jugular vein leaves the anterior triangle of the neck by passing deep to the SCM muscle.

Posterior to the sternal end of the clavicle, it unites with the subclavian vein to form the brachiocephalic vein. Near its termination is the inferior bulb of the jugular vein contains a bicuspid valve similar to that of the subclavian vein. The deep cervical lymph nodes lie along the course of the internal jugular vein, mostly lateral and posterior. Tributaries of the Internal Jugular Vein (p. 807) This large vein is joined at its origin by the: inferior petrosal sinus, the facial, lingual, pharyngeal, superior and middle thyroid veins, and often the occipital vein. Carotid Arteries Carotid Arteries Sign Up for Our Free Newsletters Thanks, You're in! Health Tip of the Day Recipe of the Day There was an error. Please try again. Please select a newsletter. Please enter a valid email address. Did you mean ?

Question: Which artery supplies blood to the head and brain?
Answer: CAROTID